The present invention relates to a process for producing bituminous surfacing, wherein a solids mix is mixed with a bituminous binder in the flowable state, the mix formed is applied to the foundation, which is to be provided with the bituminous surfacing, and is then compacted. The invention also relates to bituminous surfacing produced by this process and to a hot plant mix for carrying out the process.
When producing bituminous surfacing, as is known, a solids mix is mixed with a bituminous binder. This mix is also called hot plant mix--as long as the binder is liquid in a manner of speaking. As a rule, the term "solids mix" is to be understood as a mixture of essentially different fractions of gravel and/or chippings and of screenings, whilst the term "bituminous binder" is to be understood as bitumen, tar or a mixture of these two.
As is known, such a binder has the property, at elevated temperature, of possessing a flowability which is comparable to that of a liquid and which decreases with falling temperature, but is never completely lost.
In producing bituminous surfacing, the hot plant mix mentioned above is supplied in situ or--as is more often the case--is delivered to the site in the hot state as a semi-finished product, as it were. On site, the hot plant mix is applied to the foundation (as a rule a gravel bed or a crushed stone bed) which is to be provided with bituminous surfacing, for example by means of a finishing machine, and is then compacted. Compacting is effected by exerting a pressure (for example by means of rollers) which forces the particles of the solids mix closer together and thus presses the bituminous binder into the interspaces which have remained free.
It is known that the surface of bituminous surfacing, which is subjected to loading again and again in one and the same area (for example along the tracks of vehicle wheels), is correspondingly deformed. This deformation is to be ascribed not only to wear but also to a plastic deformation of the surfacing, which deformation takes place only very slowly but sooner or later leads to fracture or crumbling of the bituminous surfacing, if the latter is not of sufficient depth.